What does “:” (a single colon) mean in “Klass:method(p)”?

问题

Today I saw this code:

void CameraTree::dragMoveEvent(QDragMoveEvent *event)
{
    QTreeWidget:dragMoveEvent(event);
}

I think the above code is wrong. But:

void CameraTree::dragMoveEvent(QDragMoveEvent *event)
{
   dragMoveEvent(event);//infinite recursion???
}

void CameraTree::dragMoveEvent(QDragMoveEvent *event)
{
    QTreeWidget::dragMoveEvent(event);
    // I understand is called dragMoveEvent in class QTreeWidget.
    // But dragMoveEvent is not static??
}

And only warned "unused label QTreeWidget", compiled successfully. What does : mean?

回答1:

The intended code was probably QTreeWidget::dragMoveEvent(event); as you thought. QTreeWidget::dragMoveEvent(event) does not need to be static to be invoked from CameraTree if CameraTree inherits from QTreeWidget. In C++, labels are indicated with a single colon :. The reason QTreeWidget:dragMoveEvent(event); compiles is because QTreeWidget: is interpreted as a label and then dragMoveEvent(event); is a recursive call.

来源：https://stackoverflow.com/questions/47149006/what-does-a-single-colon-mean-in-klassmethodp